NASA managers are postponing the upcoming Orbital Sciences commercial cargo resupply mission to the International Space Station to proceed with a series of spacewalks to replace a faulty pump module on the space station.

NASA Television will air a news briefing at 3 p.m. EST on Wednesday, Dec. 18 to preview the spacewalks.

Orbital Sciences' Cygnus spacecraft, atop its Antares rocket, now will launch no earlier than January. The postponement of the Antares launch will allow ample time for the station crew to focus on repairing a faulty pump module that stopped working properly on Dec. 11.

NASA currently plans for two Expedition 38 astronauts to venture outside the space station Dec. 21, 23 and 25. NASA astronauts Rick Mastracchio and Mike Hopkins will remove a pump module that has a failed valve. They will replace it with an existing spare that is stored on an external stowage platform. The pump is associated with one of the station's two external cooling loops, which circulate ammonia outside the station to keep both internal and external equipment cool. Each of the three spacewalks will begin at 7:10 a.m. and is scheduled to last six and a half hours. NASA TV coverage will begin at 6:15 a.m.

Wednesday's spacewalks preview briefing will take place from NASA's Johnson Space Center in Houston. Reporters may attend the 3 p.m. briefing at Johnson and other participating NASA centers, or ask questions by calling the Johnson newsroom at 281-483-5111 no later than 2:45 p.m. Briefers will include: